Schools and other institutions often have "multi-use" rooms, some uses of which require tables. On the other hand, there are times when tables are not needed; rather, open floor space is needed. To that end, many manufacturers of institutional furniture provide tables which fold in the middle and are stored in recessed wall pockets. And such tables employ "opposed bolt" locking bars of one type or another. Such bars provide a "pivot axis" about which the table pivots when being unfolded out of the pocket to a horizontal position or when being re-folded from the horizontal position to be stored in the pocket.
Specifically, such locking bolts are axially retractable to "clear" the side panels of the wall pocket when withdrawing the end of unfolded table from such pocket. And such bolts are extended into slots in the pocket side panels when one is preparing to re-fold the table into the pocket.
In the past, different types of mechanical arrangements have been used to extend and retract table locking bolts. One type involves a rotating handle arrangement which is located at the "pocket end" of the table and coincident with the long axis of the bolts. The handle is rotated in one direction to urge the bolts outward and in the other to retract them. Such handles are difficult to reach and to operate. And if the table is the first to be stored in a deep wall pocket, the handle is well within the pocket. One must virtually crawl into the pocket to operate such handle.
In another type, the bolts are extended and retracted using a flexible wire oriented perpendicular to the long axis of the bolts and positioned midway between such bolts. The wire is attached to the center of a flexible chain-like yoke, each end of which is coupled to the end of a separate bolt. Pulling on the wire retracts the bolts and releasing it permits the bolts to extend under spring urging. Each of the foregoing arrangements has been attended by certain problems.
For example (and with respect to the rearward or rearmost table in a wall pocket), the rotating handle in the first-described arrangement is very difficult to reach and operate, especially if a particular wall pocket stores three or four tables. For the inward-most tables, the handle is rather deep in the pocket. In the type using the flexible wire, the wire breaks rather easily and adjustment of lock bolt stroke is difficult.
Other prior art arrangements are depicted in U.S. Pat. Nos. 1,197,612 (Ditlevson); 1,174,652 (Banks); 1,273,332 (Cline) and 1,900,785 (Ashbrook). The Ditlevson patent depicts a garage door lock having a pair of retractable bolts, each of which is connected to one end of a separate toggle arm. These toggle arms are moved by forces applied thereto by two end-to-end rods. One of the two rods is supported and guided by a bracket.
The end-to-end rods are operated by a rather complex lever arrangement having several pivot points and including as a component a bellcrank-shaped lever which the patent refers to as a "bent arm lever."
The Banks patent shows a twin door latch having a pair of axially opposed, spring biased bolts operated by applying force to a pair of pivotably-pinned bell crank levers. Between each bolt and its corresponding bell crank lever, there is a connecting bar having a U-shaped yoke at either end.
The latch is operated by pushing on an operating pin which rotates the bell crank levers and retracts the bolts. When the pin is released, the bias springs return the bolts to their locking positions.
The Cline patent depicts a locking fastener arrangement for the hood of an automobile of the type having two side-lifted engine compartment covers. The fastener has a pair of relatively short axially opposed bolts, each of which is pinned to a separate link. In turn, the links are commonly pinned to a bolt-like handle which moves in a slot. Upward force applied to the handle retracts the bolts for hood opening. The fastener is re-latched manually or, perhaps, by gravity.
The Ashbrook patent (involving a rather unusual arrangement for an automatic door opener) depicts a single locking bar which is spring biased open but held in the "door locked" position by a curved operating lever pinned at its center. One end of the lever had an aperture through it to receive the arm portion of an L-shaped lever, the other end of which protrudes through the door to the exterior.
In use, a vehicle driver runs the vehicle against the outer end of the L-shaped lever to release the operating lever. Such lever is then pivoted (through a linkage) by the springs to an unlatched position. Presumably, the mechanism is reset manually after each use.